Design and optimization of a multi-level wasted heat recovery system for a natural gas-based gas turbine cycle; comprehensive exergy and economic analyses

The increasing demand for power and the imperative of harnessing wasted heat to optimize power systems have motivated this current study. The main goal is conceptualizing an innovative multi-generation plant fueled by natural gas, which ingeniously integrates four distinct cycles: steam Rankine, absorption power, ejector refrigeration, and proton exchange membrane electrolyzer. This integration is synergistically coupled with a gas turbine to elevate overall system performance significantly. The investigation extends to the thorough examination, including the system's energy, exergy, and economic attributes, facilitating an all-encompassing assessment of the newly conceived plant's efficiency. Through a meticulous parametric inquiry, the study scrutinizes the influence of various parameters on the operational prowess of the system. Moreover, the quest for optimum performance unfolds through a multi-objective optimization process conducted across three distinct scenarios. Regarding the outcomes, at the base operating conditions, the novel system exhibits the capacity to yield 3,896.6 kW of net power, additionally generating a cooling load of 77.7 kW and producing 0.22 kg/h of hydrogen. Notably, it attains an exergy efficiency of 47.1 %, with the combined unit cost of products and a commendable payback period measuring at 9.16 $/GJ and 1.4 years, respectively, under baseline conditions. The preeminent role in exergy destruction is attributed to the gas turbine cycle, accounting for 88.59 % of the total, while the highest share of the total investment cost is allocated to the turbines. The pinnacle of optimal performance is realized in a state wherein the system achieves its zenith in terms of efficiency and output, reflecting the culmination of meticulous design and analysis.